The BRMP has recommended that a number of biological response modifiers be evaluated for both biological effectiveness and therapeutic potential. Among the agents considered as potentially effective is Interleukin-2 (IL-2), formerly referred to has T-cell growth factor (TCGF). The presence of this lymphokine has been shown to be a requirement for T-cell proliferation in vitro and appears to have important effects on T-cell and natural killer (NK) cell proliferationand function in vivo.